Integrated circuit (“IC”) manufacturers are constantly striving to lower their manufacturing costs by increasing the number of semiconductor devices that can be manufactured from a single wafer, i.e., increasing the device density. The formation of various integrated circuit structures from a semiconductor wafer often relies on lithographic processes, sometimes referred to as photolithography. For instance, patterns can be formed from a photoresist layer by passing radiation through a mask (or reticle) having a pattern that will be imaged onto the photoresist layer. As a result, the pattern is transferred to the photoresist layer. For a positive photoresist, in areas where the photoresist is sufficiently exposed and after a development cycle, portions of the photoresist material become soluble such that they can be removed to selectively expose an underlying layer (e.g., a semiconductor layer, a metal or metal containing layer, a dielectric layer, etc.). The portions of the photoresist layer that are not exposed to a threshold amount of radiation will not be removed and remain to protect the underlying layer. The exposed portions of the underlying layer can then be etched (e.g., by using a chemical wet etch or a dry reactive ion etch (RIE)) such that the pattern formed from the photoresist layer is transferred to the underlying layer. Alternatively, the photoresist layer can be used to block dopant implantation into the protected portions of the underlying layer or to retard reaction of the protected portions of the underlying layer. Thereafter, the remaining portions of the photoresist layer can be stripped.
Because of the desire to increase device density, there is a need to increase the resolution capability of lithography systems. One promising alternative to conventional optical lithography is a next-generation lithography technique known as immersion lithography. In immersion lithography, an immersion lithography medium is placed between the final lens of an imaging system and a photosensitive material (e.g., a photoresist) on the surface of a semiconductor wafer. The immersion lithography medium replaces an air (or other gas) gap that is conventionally present between the final lens of a conventional dry lithography imaging system and the wafer. The desired pattern of radiation is transmitted through the immersion lithography medium to the photosensitive material.
A drawback with immersion lithography is that photosensitive films, such as photoresist, are hydrophobic. Similarly, protective topcoat films formed on a photosensitive film are also hydrophobic. When these films are placed in an immersion lithography medium, water present in the immersion lithography medium is repelled owing to their hydrophobic nature. However, it is desirable for water to coat these films so that bubbles are not formed between the lens of the immersion lithography system and the wafer during exposure of the photosensitive film to radiation. In addition, components of photosensitive and topcoat films may leach into the aqueous immersion lithography medium and cause defects. These defects can be chemical residues or printing defects due to contamination that alters the optical properties of the immersion fluid such that the image is distorted during exposure.
Accordingly, it would be advantageous to have a method and solution for tuning surface energies of materials used in manufacturing an integrated circuit. It would be of further advantage for the method and solution to be cost efficient and suitable for use with a variety of materials.